COVID vaccine side effects tend to be pretty predictable: a sore arm here, a headache there, sometimes fatigue or a minor fever. But doctors are now acknowledging a far stranger side effect, which they say patients are anecdotally sharing following their shots. The phenomenon, they say, arrives the night you get the COVID vaccine and tends to be more frequently reported after the second dose. Read on to find out which strange side effect may strike on the night of your vaccine, and for another side effect that’s baffling the medical world, check out The Strange New COVID Vaccine Side Effect That’s Confusing Even Doctors. You may experience strange or vivid dreams. Patients have been reporting a highly unanticipated side effect following the COVID vaccine: vivid dreams. CBS4 Medical Editor, David Hnida, MD, recently reported that he’s heard several of these patient stories in the wild, noting that many of the anecdotes he’s heard personally seem to involve “outer space.”“Flying to the moon, planting the flag on the moon. Even somebody going out and taking Abraham Lincoln to get a Big Mac and having the staff want him to autograph the bills,” said Hnida. “We really think it has something to do with the immune response.” And for more up-to-date COVID news delivered straight to your inbox, sign up for our daily newsletter. It may happen because the vaccine interrupts our sleep cycles. The phenomenon hasn’t been formally researched, so it’s hard to say conclusively why some people are experiencing such strange dreams after their vaccinations. But doctors speculate that as your immune response surges in reaction to the shot and triggers other side effects, those may disrupt your sleep cycle, ultimately making your dreams more memorable.“They’re expecting to experience fever, muscle pain, headache and they’re probably not sleeping well,” Dan Shade, MD, a sleep specialist at the Allegheny Health Network, told a local CBS Pittsburgh affiliate. “The most common reason we remember dreams is our sleep is disrupted.”And for more on what not to take ahead of your shot, check out This Common Medication Can Make Your Vaccine Less Effective, Study Says. People have been sharing their strange dreams after getting vaccinated on social media. Many vaccine recipients have taken to Twitter to report their own strange vaccine dreams after real estate attorney Richard Vetstein reported his experience on the platform. “Aside from the flu-like symptoms and general ‘vax fog’ for 24-36 hours, the strangest thing were [sic] the weird dreams.” He followed up by explaining in a second post, “One of them was, I saved a Belgian town from the Nazis, so that was interesting. The other one, I was on the Titanic… You wake up, and you’re like, ‘what was that?’” he wrote.As Vetstein’s post gained traction, more people chimed in to report their own experiences and others marveled that they hadn’t made the connection between the dreams and the vaccine until seeing Vetstein’s tweet. “I have a whole text thread with my besties about my weird dreams last week and I never tied it to the vaccine which I got at the same time!” said one user. And for one thing you shouldn’t do after you get vaccinated, beware that Doing This After Your Vaccine Can Make Side Effects Worse, Doctors Say. They’re only temporary, so they shouldn’t concern you too much. Sure, your dreams may leave you feeling a little unsettled or confused, but rest assured that your vivid dreams are most likely nothing to worry about. Doctors say that whether they’re the physiological result of your immune system or the psychological culmination of a long and arduous year, they haven’t been linked with any other negative effects and, as Hnida noted, “they are temporary.”“I think the bottom line, if you have anything weird going on, the most important thing to know is you’re not alone and they are generally not of great concern,” he said. And for more on a certain COVID vaccine’s side effects, check out The One Side Effect That’s Much More Common With Pfizer, Data Shows.